Sailboat centerboard



United States Patent [56] References Cited UNITED STATES PATENTS 768,085 8/l904 Stromborg l 14/1 36X FOREIGN PATENTS 38.812 1/1924 Norway .4 ll4/l 28 Primary Examiner-Trygve M. Blix ABSTRACT: A sailboat centerboard having a shape capable of generating a net hydrofoil effect. Because of the shape of the centerboard a force is generated by the motion of the boat through the water which acts so as to right the boat.

SAILBOAT CENTERBOARD This invention relates to a sailboat centerboard having a shape capable of generating a net hydrofoil effect. The effect may be to either side or nil as desired.

In strong winds when a sailboat is beating, reaching, or even running, its speed is limited by its list. That is, one cannot take full advantage of the wind available because the boat will tip over.

l have discovered that this difficulty can be remedied by means of a centerboard which can exert a force which will tend to right the boat. The magnitude of the force is proportional to the speed of the centerboard through the water. This force enables one to take better advantage of high winds and lessens the likelihood that the boat will tip over.

While I do not wish to be bound by theories, I believe that my centerboard operates on the same principle that generates lift in an airplane wing, that is, as a result of Bernoulli's Principle. This Principle implies that the force of a fluid on a surface over which it flows is inversely proportional to the speed of the fluid. If the surface is shaped so that fluid passing over one side must move a greater distance, and therefore faster than the fluid passing over the other side, the force of the fluid on one side will be less and the surface will move laterally.

Collectively, and regardless of why it works, my centerboard has a net hydrofoil effect" by which I mean that when my centerboard is passed through water a force will be generated which is perpendicular to the direction of motion; this force is due to the pressure on one side of the centerboard being greater than the pressure on the other side.

The accompanying drawings illustrate certain presently preferred means for accomplishing the effects just described.

FIG. 1 is a plan view of the portion of a sailboat containing the centerboard, the bow of the boat being towards the top of the drawing;

FIG. 2 is a side view of a centerboard according to this invention.

In FIG. I, a portion of a sailboat 1 is provided with centerboard box 2. In this box is placed a centerboard (see FIG. 2) which has a leading surface 3 and a trailing surface 4. These two surfaces are movably hinged together by means of hinge pin 5. A support 6 holds the centerboard in the centerboard box and keeps the leading surface in the center of the box. Pin 7 has cord 8 affixed thereto. This cord can be tied to any of the pins 9 thereby controlling the position of trailing surface 4.

In the position shown in FIG. I the net hydrofoil effect is a force to the right. While I do not wish to be Iimitedby theories, I' believe that this effect is due to water passing to the right of the centerboard travelling farther than water passing to the left. Because it travels farther, it exerts less pressure and the net effect is a force to the right. Thus, the position shown in FIG. 1 would be used for a starboard list. Since the leading and trailing surfaces are laterally symmetrical a corresponding position may be obtained for a port list by moving the trailing surface to the right and tying the cord to a pin on the right. A position in the center would be used when no net hydrofoil effect is desired. Many other means of obtaining a net hydrofoil effect will be apparent to those skilled in the art of hydrodynamics and the drawings should be regarded as only illustrative of one embodiment of this invention.

Although one may use a right and left" centerboard or turn a centerboard upside down for starboard and port list, preferably the centerboard is constructed so that the net hydrofoil effect can be starboard, port, or nil as desired by simply altering the shape of the centerboard as is illustrated by the drawings. centerboard as used herein means not only the conventional centerboard, but also any portion of the keel which is used according to this invention to generate a net hydrofoil effect. The centerboard is preferably located at the lateral center of the boat; more than one centerboard capable of generating a net hydrofoil effect may be used simultaneously if desired.

Iclaim: 1. A sailboat centerboard disposed within a centerboard trailing surface on said axis, and means secured to the top of said trailing surface and box for holding said trailing surface in a fixed position. 

